1. Field of the Invention
The present invention relates to a digital data recording method and apparatus that separates digital data in units of constant or variable lengths, and records the separated digital data as a plurality of data blocks on a magnetic tape, a reproducing apparatus for reproducing the recorded digital data, and the magnetic tape on which the digital data are recorded.
2. Description of the Related Art
A conventional helical-scanning recording-and-reproducing system is known that uses a rotary head to form recording tracks inclined to the feeding direction of a magnetic tape as a recording medium so that digital data such as audio data and video data are recorded or reproduced.
In the helical-scanning recording-and-reproducing system, the digital data recorded on the magnetic tape are normally separated in units of predetermined length, and control data including at least a synchronizing signal and address information are added to each separated digital data unit, whereby a plurality of data blocks is formed. The digital data are processed using one data block as the minimum data unit.
The control data added to each data block is called a xe2x80x9cheaderxe2x80x9d, and is normally positioned at the head of each data block. The digital data are reproduced by initially reading the control data at the head of each data block, recognizing, based on the read control data, the head and position of each data block, reading data such as audio data and video data, and performing post-stage signal processing based on the control data so that the read data are recomposed to generate reproduced data.
Recently, a so-called xe2x80x9cnon-tracking reproducing methodxe2x80x9d has been proposed as a type of the above-described digital data reproduction. The non-tracking reproducing method recomposes correctly read data by using a reproducing magnetic head to perform scanning at a speed double that of the relative movement of the magnetic head and the magnetic tape in the recording mode, whereby the need for controlling the reproducing magnetic head to precisely trace recording tracks is eliminated.
In the non-tracking reproducing method, the reproducing magnetic head may fail to precisely trace the recording tracks, and may scan more than one recording track at the same time by skewing across them. This causes the order of data blocks in the recording mode to differ from an order of data blocks in the reproduction mode. Accordingly, in the non-tracking reproducing method, data that were correctly read by scanning using the reproducing magnetic head are temporarily stored in a memory, and data are recomposed for reproduction by rearranging the stored data in the recording order, based on control data.
In the non-tracking reproducing method, only data blocks having acceptable error rates are stored in the memory as data blocks based on which recomposition is performed, and data blocks having inferior error rates are not stored in the memory.
In the non-tracking reproducing method, the error rate of the read data varies in accordance with the distance at which the reproducing magnetic head is positioned on the recording tracks at the recording position of the read data. The reproducing magnetic head scans the recording tracks by skewing. Thus, data constituting one single data block may include acceptable error rates and inferior error rates. The single data block has the greatest difference in error rates in the head and end thereof.
In the non-tracking reproducing method, the error rates of the read data block are evaluated based on the error rate of the control data at the head of each data block. Thus, in the case where the error rate of the. control data is inferior, the error rates of the entire data block are regarded as inferior, even when the end portion of the data block has an acceptable error rate. This may prevent the entire data block from being stored in the memory. Conversely, in the case where the error rate of the control data is acceptable, the error rate of the entire data block is regarded as acceptable, even when the end portion of the data block has an inferior rate. Thus, data having an inferior error rate may be stored in the memory.
Therefore, the non-tracking reproducing method has a problem in that the data utilizing efficiency deteriorates and the reliability of the reproduced data may be reduced.
Accordingly, it is an object of the present invention to provide a digital data recording method and apparatus for suppressing a decrease in data utilizing efficiency and for obtaining highly reliable reproduced data, a reproducing apparatus for reproducing highly reliable digital data while suppressing a decrease in data utilizing efficiency, and a magnetic tape on which digital data for suppressing a decrease in data utilizing efficiency and for improving the reliability of reproduced data are recorded.
To this end, according to an aspect of the present invention, the foregoing object is achieved through provision of a digital data recording method for recording, on a magnetic tape, digital data comprised of a plurality of data blocks. Each data block has a known length and includes control data including at least a synchronizing signal and address information, and the digital data recording method records the control data at a position excluding the opposite ends of each data block.
According to another aspect of the present invention, the foregoing object is achieved through provision of a recording apparatus including a data writer for recording digital data on a magnetic tape by using a recording head and the magnetic tape so that the recording head and the magnetic tape are moved with respect to each other, and a data supplier for supplying the data writer with the digital data as a plurality of data blocks separated into units having known lengths. The data blocks each include control data including at least a synchronizing signal and address information, and the control data is recorded at a position excluding the opposite ends of each data block.
According to a further aspect of the present invention, the foregoing object is achieved through provision of a reproducing apparatus including a data reader for causing a reproducing magnetic head to scan a magnetic tape so that digital data recorded on the magnetic tape are read, and a signal processor for generating reproduced data by implementing signal processing for the digital data read by the data reader. The digital data read by the data reader are recorded on the magnetic tape as a plurality of data blocks which are separated into units having known lengths. The data blocks each include control data including at least a synchronizing signal and address information, and the control data is recorded at a position excluding the opposite ends,of each data block.
Preferably, the signal processor generates the reproduced data by temporarily storing the digital data read by the data reader, and recomposing the digital data based on the address information of each data block.
According to yet another aspect of the present invention, the foregoing object is achieved through provision of a magnetic tape on which digital data as a plurality of data blocks separated into units having known lengths are recorded for recording tracks inclined with respect to the direction of scanning. The data blocks each include control data including at least a synchronizing signal and address information, and the control data is recorded at a position excluding the opposite ends of each data block.
According to the present invention, control data based on which error rates of each data block is evaluated is added to a position of the data block excluding the opposite ends of the data block. Therefore, even in the case where the error rate of data at the head of the data block differs from the error rate of data at the end of the data block, almost the average of error rates of data in the data block is evaluated such that a reproducing magnetic head scans recording tracks by skewing.
Therefore, by using the present invention to record digital data, the data utilizing efficiency in reproduction of the digital data can be increased, and the reliability of reproduced data can be improved.